They're usable and intuitive. Circles don't feel tacked on like lists. It took me a long time to figure out how to even use lists. Google+ schema is based around your Circles. By default, you are just posting to the Circle.

I'm not worried about it going away. It's actually getting heavy usage in the professional areas.

What he said. If you use Google+ you know it's not going anywhere. The popularity with photographers alone is enough to justify its existence, but on top of that it makes a fantastic news stream once you've setup your Following circle.

They're usable and intuitive. Circles don't feel tacked on like lists. It took me a long time to figure out how to even use lists. Google+ schema is based around your Circles. By default, you are just posting to the Circle.

I'm not worried about it going away. It's actually getting heavy usage in the professional areas.

I'm not sure I can defend the entirety of Google+, but the whole "circles" thing is fantastic and 100X better than what Facebook allows. I'm definitely not the social butterfly/narcissist that social networks cater to, however I love being able to have small groups of people who I can share certain things with as they pop into my head or into my life. If I find a game I like, I have no interest in sharing that with the world; what do they care what game I like. Nor do I care to have my parents or kids see it. But I do have a group of "gamer friends" who might be legitimately interested and the circles idea makes that easy. Same thing if I take a picture of my kids at some event. My parents and other relatives might have fun with that image, but I don't care to share that with my gamer friends and definitely not the public as a whole.

If Google+ really does bite the bullet, I'll miss it. Maybe I'll be the only one, though...